Would someone please tell me what "summing" is.
From: Association for Recorded Sound Discussion List [mailto:[log in to unmask]] On Behalf Of Art Shifrin
Sent: Monday, April 23, 2012 12:08 PM
To: [log in to unmask]
Subject: [ARSCLIST] differentiating groove walls' noises
It's worthwhile to check if one of the two outputs of a monaural goove is, for a given side consistently inferior or superior. I just did another early 78.3 (rounded off) lateral cut lacquer (1934) for Niel Shell (Nat Shilkret was one of his Grandfathers). The two sides were, thankfully not
gouged by prior playings with steel needles. But it had been played
multiple times on those heavily tracking early systems. One of the outputs was dramatically less noisy than the other.
For vertical cut grooves, a method that occasionally (but not consistently) is beneficial is to also digitize both outputs. Keeping the eq. flat, then apply your best available de-clicker to the two channel digital file. THEN sum them (with one channel 180 out). When summing, interactively set the two levels for a maximum lateral noise null. Whether done with early stage declicking or not, always check audibly and or visually. You'll often find that the two levels are NOT @ unity. Assuming that your preamp & cartridge combo is properly set up, then when the level 'discrepancy' occurs, that indicates that the cutter was not functioning on a precisely vertical plane. For lateral grooves, with the critical difference being that the two outputs are nominally in phase, the comparable nulling is done to suppress the vertical component.
For grooves that are intentionally neither vertical nor lateral (i.e. Arto 78s...with their audacious knock off of Victor's "batwing' label), it's anything goes for selecting & possibly mixing outputs for the best possible results.
AFTER the nulling is performed and two channels mixed together, then apply eq. et. al.
Art (Shiffy) Shifrin